1. Field of the Invention
The invention relates to an adhesive cream composition.
2. Prior Art
Many commercial adhesive cream compositions for prosthetic teeth are based on a mixture of refined paraffins, water-soluble cellulose derivative polymers and alkyl vinyl ether/maleic acid anhydride copolymers. Conventionally, mineral oils and mineral fats, in particular Vaseline, are used. Mineral oils and mineral fats generally constitute approximately 40% by weight or more of the adhesive cream composition.
Since an adhesive cream slowly dissolves in the mouth during use, on the one hand there is the possibility that components of the adhesive cream enter the body via the mucous membranes of the mouth and pharynx and, on the other hand, components reach the digestive tract with the saliva and the food and may subsequently become distributed throughout the body. The basic components of Vaseline and mineral oil are not completely harmless according to the most recent results of research. Vaseline, for example, appears to promote blastomycosis conditions in newborn babies. Consequently, negative effects in adults cannot be excluded. Caution appears to be demanded particularly in the regular use of mineral oils on mucous membranes. Therefore, a replacement for mineral oils and mineral fats would be desirable.
In order to improve adhesion, zinc-containing substances are generally added. Such commercial adhesive cream products have a zinc content of from 1.7 to 3.4% by weight according to in-house analyses. In document U.S. Pat. No. 4,758,630, a zinc content of from 1 to 2.4% by weight of the total amount of adhesive cream composition is recommended. Recently, it has also become known that greater absorption of zinc compounds by the organism which had previously been thought to be harmless sometimes causes irreversible symptoms of poisoning. With regular use, therefore, the zinc compounds in the adhesive cream could have similar effects. In order to prevent toxic symptoms in tooth prosthesis wearers, there is a need for an adhesive cream formulation which also has excellent wearing properties and storability with addition of zinc compounds which is reduced or dispensed with.
Furthermore, commercial base products which are used in the production of adhesive creams in any case contain traces of zinc impurities such as, for example, Gantrez® MS955, a methyl vinyl ether/maleic acid anhydride copolymer which is often used in the production of adhesive creams. Analyses have shown that this base product contains 4.8 mg of zinc per kilogram. As a result, a content of approximately 2 ppm of zinc, but a maximum of 4.8 ppm of zinc, may be anticipated in an adhesive cream produced therewith. However, the proportion of zinc compounds which may be contained in such base products is far lower than that which is measured—as mentioned above—in commercial adhesive creams and originates from selective addition.
If currently existing formulations with a methyl vinyl ether/maleic acid anhydride copolymer could be modified in such a manner that it is possible to dispense, partially, or completely, with mineral oils and/or Vaseline and additionally included zinc compounds, there would result a product which can be regarded as being harmless to health. In particular the use of plant oils and fats would correspond to the current health consciousness of consumers.
The contents and the quantitative relationships determine the properties of an adhesive cream. The properties include, for example, the adhesion strength, the adhesion duration, the wearing comfort, the taste, the consistency, the stability, etcetera. In order to adjust the adhesion parameters such as adhesion duration and adhesion strength, a given proportion of Zn2+ compounds is added in commercial products on a mineral oil basis. The adhesion strength and the adhesion duration are positively influenced by the addition of zinc compounds according to document U.S. Pat. No. 4,758,630 and, consequently, the addition of zinc compounds is of great significance to the usability of the adhesive cream.
As mentioned above, paraffins such as refined mineral oils and fats (Vaseline) are used in many commercial adhesive creams. These are admixtures of saturated hydrocarbons having the general molecular formula CnH2n+2, this involving liquid products (oils) or greasy to solid products (fats) in accordance with the distillation degree. The mineral oil admixtures and fats which are used in cosmetics and medicine also consist of practically exclusively saturated hydrocarbons. The purity of the admixtures depends on the degree of refinement. The degree of refinement is high for cosmetic and medical use. It is thereby intended to be ensured that carcinogenically acting polycyclical aromatic hydrocarbons are removed from the admixture as completely as possible.
Mineral oils and fats are often used as bases of skin adhesive creams, the effect thereof being graded differently in this instance. Acknowledged groups of experts are of the opinion that paraffins can prevent the natural regulation mechanisms of the human body. In particular, they can accumulate in the liver, kidney and lymph nodes. However, there is uncertainty as to whether the paraffins can penetrate the skin. It is generally assumed that paraffins do not penetrate the skin in the case of topical application and therefore there is also no risk from those substances. Cosmetic skin adhesive creams having oils and fats have been on the market for many years. In the case of use in adhesive creams, however, there is an increased probability that paraffinic components will be absorbed directly by the body via the digestion. Document U.S. Pat. No. 5,561,177 discloses an adhesive cream formulation which is produced on the basis of plant oils. Accordingly, oils which particularly contain triglycerides of saturated fatty acids can be successfully used. Those triglycerides further have carbon chains of medium length, that is to say, chains having 8 or 10 carbon atoms in the fatty acid radical, which do not correspond to the typical fatty acid range of plant oils and fats (C12-C20). The use of oils which contain unsaturated fatty acids is not recommended. According to U.S. Pat. No. 5,561,177, oils which contain unsaturated fatty acid esters have the disadvantage that they become unstable at high temperatures or after being stored for a given time. Furthermore, adhesive creams which contain such oils are less solid owing to the unsaturated double-bonds present, that is to say, too liquid to be used as an adhesive cream.